Nanoscale electronic circuits offer the possibility of high density, high speed, and low cost, compared to current devices. However, a major difficulty in nanoscale circuits is in establishing communication circuitry for input and output. Using multiplexers and demultiplexers as the interfacial circuits can address this problem. For example, FIG. 1 shows a basic multiplexer circuit 100, in which eight nanowires (marked as 1-8) can be addressed by three addressing wires (marked as A, B, and C). The dot at each cross point is a molecule switch such as a two-way AND element, which can be a resistor, diode, or a transistor. With the multiplexer 100 shown in FIG. 1, only one of the nanowires will be addressed by each combination of signals on A, B, and C (e.g., 1, 1, 0 for A, B, C, respectively, will address the nanowire 7). In general, such multiplexer/demultiplexer circuits allow n wires to address 2n nanowires, which can establish efficient interfacial circuitry for nanoscale circuits.
Forming multiplexers/demultiplexers (or other circuits) requires the ability to selectively connect or disconnect nanowires and addressing wires at each cross point. Unfortunately, fabricating this precise pattern of logic elements at the intersections is very difficult at the nanometer scale.
One approach combines lithographic patterning for the more significant bits of the addresses with random connections for the less significant bits, as disclosed in commonly-assigned U.S. Pat. No. 6,256,767, by Kuekes et al., issued Jul. 3, 2001, entitled “DEMULTIPLEXER FOR A MOLECULAR WIRE CROSSBAR NETWORK (MWCN DEMUX)”. U.S. Pat. No. 6,256,767 is fully incorporated herein by reference. In FIG. 1, addressing wire A specifies the most significant bit of the address and wire C specifies the least significant. As shown in FIG. 1, the more significant bits of the address involve large groups of adjacent nanowires with the same connections.
When sufficiently large, the groups can be created by patterns specified by conventional techniques such as photolithography. The less significant bits, on the other hand, require precise connections alternating on a fine scale, beyond current capabilities to precisely fabricate. The previous proposals address this problem by replacing precise connections with methods that make connections randomly, i.e., without precise control of their locations. This randomness precludes creating multiplexer circuits with the precise desired pattern of connections (e.g., as shown in FIG. 1). Nevertheless, the previous proposals show that adding a certain number of extra addressing wires ensures a high probability of unique addresses for the nanowires. In other words, the added redundancies may provide a high probability of correct functionality for the circuit. While these extra wires enable constructing a reliable interface circuit, they also disadvantageously increase the overall size of the circuit.
Therefore, current technologies are limited in their capabilities and suffer from at least the above constraints.